Converter for producing controlled atmosphere for heat treating

ABSTRACT

Air and oxidizable gas are introduced into a conduit comprising a silicon carbide tube which is electrically heated, thereby promoting burning or oxidation of the oxidizable gases. A screwshaped baffle is provided interiorly of the conduit to insure proper mixing of the air and other gas.

United States Patent Edward J McCrink East Lake Street, Northlake, 111. 60164 40,160

May 25, 1970 Jan. 4, 1972 Inventor Appl. No. Filed Patented CONVERTER FOR PRODUCING CONTROLLED ATMOSPHERE FOR HEAT TREATING 4 Claims, 4 Drawing Figs.

us. Cl 219/368, 13/25,165/179, 219/374, 219/380, 338/294 Int. Cl 1105b 3/02, H0513 3/12, 1105b 3/42 Field of Search 13/20, 25; /28 F; /177, 179; 219/296, 299-305, 359, 366-370, 373, 374, 380, 406; 431/350, 354, 355; 338/234, 236, 294

References Cited UNITED STATES PATENTS 10/1919 Thomson 1 /1945 Fahrenwa1d.. 5/1912 Matteson 9/1941 Williams 3/1913 Segelken 1/1943 Gillespie... 4/1963 Wagner 3/1964 Buechner Primary Examiner-A. D. Pellinen Attorney-Olson, Trexler, Wolters & Bushnell 219/301 43l/3S4X 219/299X ABSTRACT: Air and oxidizable gas are introduced into a conduit comprising a silicon carbide tube which is electrically heated, thereby promoting burning or oxidation of the oxidizable gases. A screw-shaped baffle is provided interiorly of the conduit to insure proper mixing of the air and other gas.

PATENTEUJAN 4m Q m6 355 kmkkwik u WW 1 SI Www CONVERTER FOR PRODUCING CONTROLLED ATMOSPHERE FOR HEAT TREATING BACKGROUND OF THE INVENTION Many industrial processes require the heating of workpieces in a more or less inert atmosphere, specifically a nonoxidizing atmosphere. Converters for supplying inert or nonoxidizing gases are available commercially, but are quite expensive.

OBJECTS AND BRIEF DESCRIPTION Accordingly, it is an object of the present invention to provide an atmosphere converter for providing inert or nonoxidizing gases.

Specifically, it is an object of the present invention to provide an electric resistant heating conduit in which air and one or more oxidizable gases are mixed thoroughly and heated to burn all of the oxidizable gas present, and thereby to provide inert gas as for industrial purposes.

In accordance with the present invention air and one or more oxidizable gases are discharged into a silicon carbide tube which is heated by the carrying of electric current. The tube is provided in its interior with a baffle in the form of a screw thread to promote mixing of the air and other gas.

DESCRIPTION OF THE DRAWINGS AND DETAILED DESCRIPTION Various additional objects and advantages of the present invention will be apparent from the following description when taken in connection with the accompanying drawings wherein:

FIG. 1 is a block diagram illustrating the principles of the present invention;

FIG. 2 is a longitudinal sectional view through the atmospheric converter comprising the subject matter of the present invention;

FIG. 3 is a view generally similar to FIG. 2 showing a modification of the invention; and,

FIG. 4 is a cross-sectional view as taken along the line 44 in FIG. 3.

Turning now in greater particularity to the drawings, and first to FIG. 1, there will be an atmosphere converter supplied with gas from a source 12, and also supplied with air from a source 14, which may simply be a blower from the surrounding atmosphere. The output of the converter 10 is supplied to a furnace l6 requiring an inert gas atmosphere.

Turning now to FIG. 2, the atmosphere converter 10 will be seen to comprise an elongated cylinder or tube 18 of silicon carbide, and having circumferential, radially extending flanges 20 and 22 at its inlet and outlet ends, respectively. The cylinder or tube is provided interiorly with a spiral baffle 24 of relatively long lead. The tube is provided on the outside with insulation 26 to limit escape of heat from the tube.

At the inlet end of the tube is provided with a clamp 28 about its exterior connected to an electric cable 30, while a similar clamp 32 is provided adjacent the outlet end, connected to an electric cable 34. As will be understood, the two cables are connected to opposite terminals of an electric source such as an engine driven battery or alternator. Since the cylinder is made of silicon carbide, which is a known resistance heating material, it will be recognized that the cylinder or tube can be heated to a very high temperature on the order of several hundred degrees Fahrenheit by the passage of electric current between the cables and 34. As will be appreciated, suitable controls are provided to determine the amount of current, and these may be quite conventional in nature, whereby illustration is superfluous. The spiral baflle 24 may be formed integral with the cylinder 18, thereby constituting a part of the heater, or it may be an inserted element of the same material, or of a ceramic material, held in place by any suitable means. In fact, the spiral baffle may be several separate parts butted against one another, or spaced apart by suitable spacers.

At the inlet end of the converter tube 18, a gas inlet tube 36 and an air inlet tube 38 are suitabl connected to a disc or bulkhead 40. A clamping washer 4 IS secured to the disc or bulkhead 40 by nuts and bolts 44, and suitable asbestos gaskets 46 are provided for an airtight relationship. Similarly, at the outlet end there is a pipe 48 having a circumferential radially extending flange which has a clamp washer 52 secured to it by nuts and bolts 54, thus clamping the flange 22 of the tube 18 against it. Again, suitable asbestos gaskets 56 are provided for an airtight relationship.

A suitable gas is pumped into the converter 10 through the gas inlet 36' while air is pumped in through the inlet 38. The two are mixed together with a swirling action as they pass through the tube 18, such swirling being provided by the spiral baffle 24. Since they are heated to a high temperature, the gas, which may be any suitable hydrocarbon or other oxidizable gas passes out into the outlet pipe 48 to an endothermic atmosphere which may be in a furnace or retort. The exit gases from the converter may comprise a mixture of nitrogen, carbon dioxide, water vapor, and perhaps hydrogen if the air and inlet gas are mixed in the proper proportions. Some carbon monoxide may also be present. The important thing is that there is no free oxygen whereby the article or materials heated in the furnace or retort are not oxidized.

A modification of the invention is shown in FIGS. 3 and 4. Many of the parts are similar to those heretofore shown and described, and accordingly like numerals are utilized to identify similar parts, with the addition of the suffix a. The distinction in the present instance is that a rod 58 extends along the axis of the tube 18a and is provided with spaced baffles 60, which may be of suitable metallic construction, or of ceramic or silica. The transverse baffles 60 preclude a central straight through flow path, and insure a proper swirling action as produced by the spiral baffle 240.

It is believed with proper operating temperatures, and in the absence of air, that ammonia can be dissociated in the present apparatus to provide nitrogen and hydrogen. Similarly, methane and air can be cracked to form an endothermic atmosphere.

It will now be seen that I have provided a simple and inexpensive atmospheric converter for producing an inert gas, or reducing gas mixture for use in a furnace or retort, whereby to prevent oxidation of articles or materials therein. The specific examples of the invention as herein shown and described are for illustrative purposes only. Various changes in structure will no doubt occur to those skilled in the art, and will be understood as forming a part of the present invention insofar as they fall within the spirit and scope of the appended claims.

The invention is claimed as follows:

I. A converter comprising a substantially cylindrical conduit having resistive electric conductive properties, electric connection means adjacent opposite extremities of said conduit for electric resistance heating thereof, means for supplying an oxidizable gas to said conduit, means for supplying air to said conduit, and means for mixing said gas and air in said conduit comprising a spiral baffle of electric conductive material having resistive properties within and in electric engagement with said conduit, said conduit and said baffle being heated to a high temperature by electric resistance heating.

2. A converter as set forth in claim I wherein the conduit and the baffle are made of silicon carbide.

3. A converter as set forth in claim 2 wherein said baffle is in the form of a spiral having an open center.

4. A converter as set forth in claim 3 and further including a plurality of transverse baffles spaced along the center of said spiral baffle, there being one such baffle for each turn of the spiral baffle. 

2. A converter as set forth in claim 1 wherein the conduit and the baffle are made of silicon carbide.
 3. A converter as set forth in claim 2 wherein said baffle is in the form of a spiral having an open center.
 4. A converter as set forth in claim 3 and further including a plurality of transverse baffles spaced along the center of said spiral baffle, there being one such baffle for each turn of the spiral baffle. 